Drying of herbal extract in a draft‐tube spouted bed

This work evaluates the feasibility of the draft‐tube spouted bed for drying of herbal extract. Drying runs were carried out according to a central composite design in a conical–cylindrical draft‐tube spouted bed. The variables studied were the percentage of the drying aid (ADJ), the drying gas flow rate relative to gas flow at minimum spouting ( Q / Q ms ), and the flow rate of extract fed to the system relative to the spouting gas flow rate ( W s / W g ). Colloidal silicon dioxide was the drying aid used in order to improve drying performance. Statistical analysis of the effects of processing parameters on product recovery, product accumulation in the bed, and product properties permitted the identification of parameters presenting significant effects on drying. Optimized drying conditions were related to experimental parameters as follow: high levels of the percentage of drying adjuvant (ADJ), high airflow rate relative to minimum spouting ( Q / Q ms ), and low values of the feed flow rate of the extract relative to the gas flow rate ( W s / W g ).